Get rid of as much ply as you possibly can at this stage. Many parts can have lightening holes made or dispensed with altogether and substituted with something lighter. I speak from experience! Good luck with it.

I just subscribed to this website just for the purposes of following this thread, been considering this build myself but heard mixed reviews about the flying characteristics so looking forward to hearing your results.

I was sorely tempted to build one of these when the plan was published in the 2017 Autumn Special. I have a 90mm Lander fan for 6s so I thought by eliminating all the liteply/ply, adding lots of holes and doing away with the landing gear it might actually fly (after launching it with a catapult). I think weight is the No.1 enemy with this model as Tony's prototype on 8s had a wing loading of 43oz/squ/in. which, for a dyed in the wool gilder guilder like me is scary territory! Something I did consider was using a semi-symmetrical aerofoil section which might provide more lift at a slower speed. Another deviation from the plan I thought of, was enlarging the intake area and belly cheater hole to help the fan to 'breathe'.

I might well build one at some stage in the future as it is an impressive model but in the meantime I will be following this thread with interest - and taking notes!

You have probably seen my blog on my 54" version which I built not knowing that TN was in the process of doing a 50" one. Even with a 12 blade 10s fan there was very little thrust but I had omitted the cheat hole, now done at 3x4" but when testing, a connector got sucked into the fan and blew it up. Awaiting a replacement impeller which I hope will fit.

As advised above, shed as much ply and other weighty parts as possible.

My YEP 120A esc and Rx etc are unavoidably blocking the airflow quite a bit but since it is the same as TN does it is obviously OK.

Yes, your blog on the 54in version is very interesting Martin. Probably a silly question but I assume you calibrated your ESC to ensure it was giving you 100% power? I am sure that once you get your new impeller the new cheater hole will make a huge difference to the thrust you are getting with your 10s setup. The 7.5% increase in model size will help with the wing loading too hopefully.

Just a suggestion but as the model has flaps you, (Geoff and Martin) could try 5 or 10 degrees flap (max) for take off and also droop the ailerons as well for that matter (if your Tx will do that). The added camber and extra low speed lift can only help, with a minimal drag penalty.

Hi Piers, glad you enjoyed the build blog. I certainly am getting 100% power because the esc is programmed for an EDF and the Wattmeter confirms this. I think that the main question will be the small wheels on grass rather than lack of lift. Unless previously tested in the air there is really no way of knowing if flaps make a pitch change.

I just hope that the fan I have ordered fits OK since it is supposedly a different make but looks the same in the HK pics. I would buy a new unit but cannot get 10s so my 2x 5800 5s packs would be of no use.

I agree Martin small wheels on grass produce a lot of drag unfortunately but my thinking here with the flaps is that the wing will produce lift while it is accelerating. This will unload some weight which may help the model further accelerate to rotation speed (which will be lower due to the flaps). It works with full sized aircraft but it is only a theory as far as models are concerned! I am only talking about five/ten degrees of flap, so there shouldn't be any significant trim change. It will be an experimental model on the maiden flight anyway

My apologies to Geoff for taking over his blog. I am suffering from CNC cutter envy!

I had planned to use the no4 cap head wood screws from Modelfixings. Although, I did also consider using 3mm cap screws and T nuts - not sure if they would work in beech. You could make up a tin plate with nuts soldered on and screw it to the underside. The cap heads would be easier.